Sliding support for a superconducting generator rotor

ABSTRACT

In a superconducting generator rotor, inner and outer rotor structures are rigidly connected against torsional and axial relative movement at one end of the rotor. At the opposite end of the rotor a sliding support permits relative axial movement of the inner rotor relative to the outer rotor during cool down. The sliding support connection of the inner rotor to the rotating outer rotor and stub shaft of the generator power train is closed by a flexible diaphragm which has protruding axially therefrom a plurality of integrally attached fingers. These fingers, at an outside radial surface, bear into a complementary cylindrical cavity in the end of the stub shaft having female spline receiving concavities. During thermal axial excursion incident to cool down, the fingers by sliding into and out of the spline concavities in the stub shaft accommodate relative axial movement of the inner rotor relative to the outer rotor. During on-line operation of the rotor, the fingers maintain a positive and nonsliding fit with the stub shaft so that by positive outward pressure at the fingers, slip and fretting corrosion of the fingers and stub shaft is prevented.

This invention relates to a superconducting generator rotor. Moreparticularly, the invention relates to a connection between a rotatingstub shaft of a generator power train and the rotating inner and outerrotor structures of a supercooled rotor assembly having superconductingwindings.

STATEMENT OF THE PROBLEM

Superconducting rotors placed within generators are desirable. Overall,they represent an elimination of losses in the windings of a rotor withan increase in generator efficiency of as much as 1%. Additionally, theyallow generator rotors and hence generator stators to be build to a muchsmaller dimension. This includes a reduction in weight of the overallgenerator. Moreover, when the rotor is constructed to a smallerdiameter, there is a resultant reduction of the problems encountered inhigh speed rotating rotors.

Superconducting rotors consist of two separate parts. Outermost there isa damper shield and damper shield support. Innermost there is an innerrotor structure including the superconducting windings or coils immersedwithin a helium refrigerated annulus. This helium refrigerated annulustypically maintains the temperature of the superconducting coils at 4.3°Kelvin or below so that superconductivity takes place.

The other damper shield and damper shield support serve two functions.First, they comprise the outer thermal jacket of the supercooled rotor.Second, the function of the shield is to prevent back electromotiveforces from the stator penetrating to the superconducting coils. Ifpenetration to the superconducting coils of the back electromotiveforces occurs, the coils of the windings become heated. When they areheated above 4.3° Kelvin, they become non-superconducting and thedesigned rotor field is lost.

A critical design parameter of the damper shield and damper shieldsupport is to accommodate short circuit loading of the generator stator.In such short circuit loading, the stator experiences very large currentflows with corresponding very large back electromotive forces beingplaced on the shield of the stator. This force tends to squash the outerrotor structure from its normal circular cross-section to an ellipticalcross section, while the rotor is turning at high speed. The shield mustbe highly conductive to oppose the A.C. stator flux. At the same time,the damper shield support must be very strong to resist the mechanicalimpact of the electromotive forces.

During normal operation, the inner rotor structure is first subjected to"cool down". In cool down, liquified helium is introduced into thevicinity of the superconducting coils. The inner rotor undergoessubstantial thermal contraction and resultant excursion in the axialdirection. Taking the case of a rotor 132 inches long, thermalcontraction of 3/10 inch can be anticipated. In a longer rotor on theorder of 275 inches long, thermal contraction of as much as 7/10 inchcan be anticipated.

At the same time this axial shrink is accommodated, two adverse effectson the rotor must be eliminated. First, any tendency of the inner rotorstructure to move torsionally with respect to the outer rotor structureduring operation must be resisted. Otherwise, this relative movementbetween inner and outer rotor structure will generate undesired backelectromotive forces from the damper shield to the rotor. These backelectromotive forces will heat the superconducting coils and result inloss of their supeconducting capability with correspondent loss of thedesigned rotor field.

Secondly, the power train to the inner rotor must accommodate a slidingfit. This sliding fit must not minutely move during normal rotorrotation. If a minute movement of the sliding fit occurs with eachrotation of a piece of machinery rotating at 3600 rpm, a rapid "frettingcorrosion" of the sliding parts of the joint will occur. Specifically,the joint will disintegrate with a growing red oxide which eats anddestroys the power transmitting joint along the sliding interface of thepower transmitting joint.

SUMMARY OF THE PRIOR ART

Heretofore at least one rotor end has been equipped with either flexiblediaphragms or spokes. These diaphragms or spokes, while providing asatisfactory connection for prototype rotors having relatively shortaxial lengths, are not workable for rotors having long lengths. This isbecause the diaphragm and spoke connections, when subjected to therelative thermal excursions of the inner and outer rotors have combinedbending stresses, rotational stresses and torsional stresses (especiallythose found in the critical stator short circuit parameter) exceedingthe limits of available strength of materials.

SUMMARY OF THE INVENTION

In a superconducting generator rotor, the rotor includes a cylindricalouter rotor structure for resisting mechanical and electrical forcesfrom fields in the stator and a coaxial supercooled inner rotor windingstructure to provide high field intensity with no resultant current flowlosses in the superconducting windings. These inner and outer rotorstructures are rigidly connected against torsional and axial relativemovement at one end of the rotor. At the opposite end of the rotor thesliding support connection of this invention is required. This slidingsupport permits relative axial movement of the inner rotor relative tothe outer rotor during cool down. At the same time the sliding supportresists slip and fretting corrosion during normal operating conditionsall without relative torsional movement between the inner and outerrotor assemblies. The sliding support connection of the inner rotor tothe rotating outer rotor and stub shaft of the generator power train isclosed by a flexible diaphragm which has protruding axially therefrom aplurality of integrally attached fingers. These fingers, at an outsideradial surface, bear into a complementary cylindrical cavity in the endof the stub shaft having female spline receiving concavities. Thefingers on their inside dimension define a frustroconical surface whichbears against a spring loaded frustroconical mandrel, preferably loadedby a Belleville sping. During thermal axial excursion incident to cooldown, the fingers by sliding into and out of the spline concavities inthe stub shaft accommodate relative axial movement of the inner rotorrelative to the outer rotor. During on-line operation of the rotor, thefingers maintain a positive and nonsliding fit with the stub shaft sothat by positive outward pressure at the fingers, slip and frettingcorrosion of the fingers and stub is prevented. All necessary rotationalflexure of the inner rotor is taken by the flexible diaphragm closingthe inner rotor.

OTHER OBJECTS AND ADVANTAGES OF THE INVENTION

An object of this invention is to provide a torsionally stiff and yetsliding inner and outer rotor connection to the drive train of agenerator. Accordingly, the drive train is rigidly connected to theouter rotor structure and provided with a cylindrical, axiallysymmetrical concavity exposed to the inner rotor. This concavity hasseries of axially extending female spline receiving concavities. Biasedmale splines from the inner rotor structure fit into the female splineconcavity of the stub shaft to effect powered rotation of the innerrotor structure.

An advantage of the sliding finger torsional coupling of the inner rotorrelative to the outer rotor is that during cool down it provides forthermal excursion of the inner rotor relative to the outer rotor.

A further advantage of this sliding finger design is that torsionalmovement of the inner rotor relative to the outer rotor during on-lineoperation of the supercooled rotor is prevented. Accordingly, backelectromotive force heating of the superconducting coil windings fromthe damper shield to the windings is prevented.

A further object of this invention is to load the torque-transmittingfingers to the inner rotor with a predetermined loading into the femalespline concavities of the stub shaft. The fingers together define afrustroconical contour. A frustroconical mandrel is spring-loaded,preferably by means of a Belleville spring against the fingers at theirinner mutual frustroconical contour. A constant loading of the fingersinto female spline concavities of the stub shaft is provided on theorder of 1000 to 2000 psi.

An advantage of the mandrel loading of the fingers is that the fingersbear against their respective concavities with such force that minutemovement of even an elongate rotor during operational rotation isprevented. Problems of fretting corrosion resistance are overcome.

An additional advantage of the biased fingers is that they provide tothe supported rotor end a rotating yet rigidly normal connection. Thisnormal connection provides a cantilevered type support to the rotor endduring rapid rotation, even though the inner rotor has axial excursion.

Yet another object of this invention is to provide to the finger ends anintegral connection to a flexible diaphragm. The flexible diaphragmforms a supporting and driving connection to the inner rotor.Accordingly, the fingers are all integrally connected to a diaphragmwhich closes the end of the inner rotor.

An advantage of the flexible diaphragm closure is that flexure of thediaphragm can take up what would otherwise be a force causing minutefinger movement at the sliding finger connectors of this invention.Assuming that under the forces of gravity an elongate rotor inevitablyhas some sag, forces tending to move the fingers can all be taken up byflexure at the diaphragm.

A further advantage of the diaphragm in combination with the slidingfingers is that the diaphragm itself is not subjected to the stresses ofthermal excursion of the inner rotor. Rather, the diaphragm, when itapproaches a loading limit due to thermal excursion, can then transmitthe force to the fingers and cause the fingers to move by axial slip intheir respective finger concavities.

Other objects, features and advantages will become more apparent afterreferring to the following specification and attached drawings in which:

FIG. 1 is a side elevation section through a generator stator and rotorwith the inner and outer rotor structure being illustrated in heavylines;

FIG. 2 is an enlarged side elevation section taken along the axis of asuperconducting generator rotor illustrating the inner and outer rotorstructure;

FIG. 3 is a side elevation axial section taken through line 3--3 of FIG.2 illustrating the stub shaft, outer rotor, and slideably connectedinner rotor;

FIG. 4 is a detail illustrating the contour of the fingers and femalefinger-receiving concavities in the stub shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a stator A is shown in section with a rotor Bdisposed axially thereof. Rotor B is driven by a stub shaft C and has atits end opposite the stub shaft a cryogenic transfer system D. Betweenthe rotor B and the stub shaft C the sliding support E for thesuperconducting generator is placed. It should be understood that thissliding support of this generator is the main point of novelty herein.However, the presence of this sliding support allows superconductingrotor B and its corresponding stator A to be elongate and to usesupercooled windings in the elongate rotor, thereby providing an overallgenerator of relatively narrow width with higher flux density than hasheretofore been used with such generators.

Stator A includes a frame 14 extending around its periphery and containstherewithin air gap type windings 15 wound between an interior glassepoxy laminated cylinder 17 and a laminated core 18. As in the case ofmost stator windings, the windings are placed in generally a toricconfiguration about the axis 20 of a rotor and define between theexterior of the rotor and the interior of the windings a small air gap22.

Because of the high flux density within the stator for the generation ofelectricity, the stator is water-cooled. Such water cooling occursthrough manifolds 24, which manifolds will not be discussed in detail.

Rotor B is located axially of the stator along a rotor axis 20. It isdriven by a stub shaft C connected to a power train at one end and isheld to the stator in paired bearings. A first bearing 26 is adjacentstub shaft C. A second bearing 27 is at the opposite end. This bearingis placed near the relatively rotatable cryogenic transfer system D.

Relatively rotatable cryogenic transfer system D transfers liquid heliumto and from the interior of rotor B. This system is fully described inarticle entitled "A Relatively Rotatable Cryogenic Transfer System"dated July 19, 1972 in a technical publication available at theMassachusetts Institute of Technology, marked MT-125J. In addition toand adjacent the transfer system D, the generator includes conventionalcollector rings 30, which rings transfer current to the field windingsof the rotor B.

Having set forth in general the construction of the stator A, stub shaftB, and having pointed out the general location of the bearings as wellas the stub shaft C and the cryogenic transfer system D, attention cannow be devoted in detail to the construction of the rotor, which isillustrated in FIG. 2.

Rotor B includes an inner rotor assembly B₁, an outer rotor assembly B₂,and a narrow spatial gap therebetween. Adjacent transfer assembly D, theinner and outer rotors are rigidly joined. The sliding support E of thisinvention is at the opposite end and provides for relative axialmovement between the inner rotor B₁ and the outer rotor B₂.

Inner rotor B₁ includes a helium chamber 40 to which transfer assembly Dcommunicates helium in a liquified form. This helium serves to keep thewindings of the generator in a superconducting state by maintaining therange of 4.3° Kelvin or lower. This temperature corresponds to -269° C.

Helium chamber 40 is bounded on either end by end walls 41, 42 and has acylinder 43 extending between the end walls. Generator windings 45 arewound about cylinder 43 and are the elements which are kept in asupercooled state for the superconducting phenomenon of this invention.Typically, the field windings 45 are of a nobium-titanium alloy cast ina copper nickel matrix. They are a standard item of manufacture of theAirco Company of New Haven, Connecticut. The field windings are boundedon their exterior by a field winding support 47. Thus, the fieldwindings are bounded on their exterior by cylindrical field windingsupport 47, and on the interior by the cylinder 43.

Connection of the cylinders 43, 47 and the field windings therebetweento the body of the rotor is accomplished by torque tubes 50, 51 ateither end. Torque tubes 50, 51 serve to prevent relative rotation ofthe windings 45 relative to the remainder of the rotor.

Between the helium chamber 40 and the end of the torque tubes there isprovided vacuum chambers 54, 55. These vacuum chambers impart a thermosbottle-like enclosure to the helium chamber 40 in a manner not unlike aconventional Dewar. Inner rotor B₁ comprises the inner section of theDewar. Outer rotor B₂ comprises the outer section of the Dewar. An airgap between the inner and outer sections maintained essentially under avacuum completes the Dewar. Helium is communicated to and from thehelium chamber 40 in the interior of the Dewar in a conduit 57 whichextends from the cryogenic transfer system E to and through wall 42 ofthe helium chamber.

It should be noted that the rotor in the vicinity of the collector rings30 and the cryogenic transfer system D is not provided with axialexcursion. Therefore, any occurring axial excursion of the rotor must betaken up in the slip joint E.

Torque tube 51 connects at end 60 to one end of an inner damper shieldsupport 62. Outer rotor B₂ includes inner damper shield support 62 whichis typically an inner support of high strength about which a dampershield 65 is supported. Exterior of damper shield 65 there is an outerdamper shield 68.

Inner damper shield 62, damper shield 65, and outer damper shield 68comprising outer rotor B₂ together perform a vital function.Specifically, this shields the rotor from back electromotive forcesproduced by the stator.

When the inner rotor and shield rotate together, the large field forceproduced by the rotor is not seen by the shield because the shieldrotates with the field. Rather, it easily penetrates through the shieldinto the stator windings 15 where it produces the desired electricalcurrent.

The back electromotive force from the stator would, in the absence ofthe damper shield 65, head toward and heat the rotor windings 45. Ifthis back electromotive force were to reach the supercooled windings 45,it would create a heat load. This heat load would take the windings outof the superconducting state and the designed current within thesuperconducting coils 45 would be immediately lost.

Damper shield 65 is a medial member between the stator and thesuperconducting windings 45 of the rotor. This damper shield "sees" theback electromotive force produced in the stator and conducts it awayfrom the rotor. Thus, the active windings 45 of the rotor in theirsuperconducting state never "see" the back electromotive force of therotor by virtue of the shield 65.

Another way to understand how the shield looks to back electromotiveforce from the stator is to say that it has a mirror effect as to statoreddy currents. This mirror acts to loop and make a back electromotiveforce which bucks out the electromotive force from the stator trying topenetrate the rotor.

The function of the inner support 62 and the outer support 68 can beunderstood. One of the critical parameters to which the generator isdesigned is that of a short current in the stator winding 15. In theevent that such a generator is shortcircuited, the stator will run witha tremendously high current for short periods of time. This high currentwill produce a back electromotive force from the stator to the rotorwhich, in spite of the presence of the damper shield 65, will tend tocrush the rotor. Understanding that the normal shape of the rotor iscircular, this back electromotive force will try to turn the circularshape of the rotor into an elliptical shape. Thus, portions of the rotorwill squeeze together while other portions will try to move furtherapart. This will occur during on-line rotation of the rotor at highspeed (the rotation here being in the range of 3600 rpm).

Damper shield 65 is designed to take away the current aspect of the backelectromotive force. While damper shield 65 functions to do this, it issubjected to tremendous mechanical forces. These mechanical forces areresisted by the inner damper shield support 62 and the outer dampershield support 68. Thus these inner and outer damper shields 62, 68produce the mechanical support for the damper shield 65. The dampershield provides for non-penetration of these high electromagnetic forcesinto the supercooled windings 45 of inner rotor B₁.

It should be understood that the rotor of this design is relativelynarrow in diameter and relatively long for the production of a highfield. According to one aspect of this invention, the rotor may be 37inches in diameter with an overall length of 160 inches. A larger rotorof up to 43 inches in diameter for a total length of 260 inches can alsobe utilized. It should be understood that with a rotor in the range of260 inches, an overall contraction in the rotor during cooldown prior tobringing the rotor on line of 7/10 inch can occur. For rotors of 160inches in length, a cooldown can produce rotor contraction of 3/10 inch.

It should be understood that between the assembly containing thewindings 45 and the damper shield, there is preferably provided a smallgap which is under a vacuum. Thus, the entirety of the rotor B consistsof two discrete assemblies. There is an inner rotor structure B₁ whichincludes the helium chamber 40, and the supercooled windings 45. Thereis also an outer rotor structure B₂ which includes the damper shield 65and its inner support 62 and outer support 68.

Regarding these inner and outer rotor assemblies, it is of paramountimportance that there be no relative torsional movement between thewindings 45 and the damper shield 65. Small torsional movement of thewindings relative to the damper shield can function to generateelectromagnetic forces in the windings 45. These electromagnetic forcesin the windings 45 can cause heating, resultant loss of thesuperconductive state, and attendant loss of the design rotor field andloss of the overall design generator load. Torque tubes 50 and 51 serveto prevent such relative rotation and provide an overall and torsionallyrigid structure to the entire length of the rotor.

The vacuum interior of vacuum chamber 54 extends exterior to the chamberto an evacuated annulus 70. Annulus 70 is separated from atmosphere by abellows 72. Bellows 72 are provided to permit axial excursion of theinner rotor relative to the outer rotor while, at the same time,permitting slip joint E of this invention to operate in a gaseousenvironment, preferably ambient atmosphere. This prevents "welding" ofthe metal interface of slip joint E which might otherwise occur in avacuum.

Having set forth the inner and outer rotor structures, a problem whichthis invention solves can now be discussed. Specifically, when the rotorB is brought on line helium is introduced interior of chamber 40. Thiscauses windings 45 to be cooled into the range of 4.3° Kelvin and causesthe windings 45 to go into a superconducting state.

Unfortunately this same cooling causes the rotor to undergo axialexcursion. Since such axial excursion is not taken up in the vicinity ofeither the collector rings 30 or the cryogenic transfer system D, itmust be taken up at the stub shaft end of the rotor assembly C.Specifically, the inner rotor assembly including superconducting coils45 will contract relative to the outer rotor assembly including thedamper shield 65 and its inner support 62 and outer support 68. Theproblem which the invention solves is how, as a practical matter, thisaxial excursion can be taken.

Vacuum chamber 54 is closed at one end by a diaphragm 80. Diaphragm 80is provided with an annulus 81, a flexible medial portion 82, and sixradially extending tines 83. Preferably, tines 83 are integral to theflexible portion of the diaphragm 82 and protrude normally therefrom allabout the axis 20 of the generator rotor and stator.

Tines 83 together form therewithin a frustroconical cavity 85.Frustroconical cavity 85 has an interior female shape which iscomplementary to an exterior frustroconical mandrel 86. Mandrel 86includes at its outermost end and bears against a Belleville spring 89.This Belleville spring 89 biases the frustroconical mandrel 86 againstthe frustroconical aperture 85 to exert a uniform outward force on thetines 83. Belleville spring 89 is held securely against mandrel 86 by anaxial bolt 90. The bolt 90 biases the mandrel with considerable force.This force provides a bias at tines 83 in the range of 1000 to 2000pounds per square inch along their finger surfaces.

Fingers 83 are generally provided with bevels 91. These bevels form themale surfaces of the tine 91. The stub shaft C is provided with interiorand mating female tined cavities 92. Tined cavities 92 include femalebevels 93. Female bevels 93 are the surfaces against which theindividual tines 83 bear during rotation of the inner and outer rotormembers.

It will be remembered that stub shaft C is rigidly connected to theouter rotor assembly including damper shield 65 and inner shield support62 and outer support 68. Likewise, the diaphragm 80 is rigidly connectedto the inner rotor including the supercooled windings 45 and the heliumchamber 40 and the vacuum chambers 54, 55.

Having set forth the construction of the mechanism, its operation can beeasily understood. It is noted that fingers 83 are cantilevered into thediaphragm. The pressure exerted on these fingers from the conicalmandrel 86 biases the fingers 83 outwardly into rigid contact with thefemale concavity and stub shaft C. Specifically, fingers 83 at surfaces91 bear with great force on female cavities 92 at complementary bevelledsurfaces 93. When the rotor B is initially brought to the supercooledstate, contraction will occur. Specifically, fingers 83 will slidewithin stub shaft C so that the fingers are partially withdrawn from theinterior of the stub shaft. When cooling has ceased, withdrawal of thefingers 83 will likewise cease.

It will be appreciated that the rotor is relatively long (in the rangeof 160 to 260 inches). Specifically, from its support at bearings 26 atone end, to bearings 27 at the opposite end, rotor B will tend to sag.This sagging will be a natural flexure under the weight of the rotorincluding its metallic parts, liquified helizm, and supercooledwindings. This weight produces from one end of the rotor to the otherend of the rotor a small degree of warp. This warp would cause relativedeflection inwardly and outwardly of the fingers. Since the rotor turnsat a speed in the range of 3600 revolutions per minute, a small fingermotion would be produced with each revolution. This small fingermovement with each revolution would cause a phenomenon known as"fretting corrosion."

In the fretting corrosion phenomenon, the fingers would undergo a minuteamount of axial slide motion with each revolution. Fingers 83 wouldslowly grind the interface between their bevelled edges 91 and thefemale bevelled edges 93 into a red dust. This red dust would be acombination of oxidation and metal fatigue. The whole joint between theinner and outer rotor at the drive shaft would collapse.

This fretting corrosion is resisted by two discrete forces. First, thefingers are provided with a bias outwardly by the mandrel 86. This biasis sufficient to overcome all tendency of the fingers to move axiallyduring rotation.

Secondly, diaphragm 80 at flexible portion 82 is provided with flexure.Necessary deflection of the rotor occurs all at the diaphragm 82. Noneof the flexure is produced at the fingers 83. The result is that duringrapid relative rotation fretting corrosion is avoided.

It should be understood that the invention described herein will admitof modification. For example, it is possible to reverse the fingers sothat they are biased inwardly rather than biased outwardly. It should benoted that in this configuration, centrifugal force would oppose thebiased fingers. Secondly, it is not necessary to have a Bellevillespring. Various combinations of leaf springs and other members could beutilized. Moreover, the joint could be reversed. The fingers could bedisposed towards the rotor rather than away from the rotor.

It should be noted that the fingers are in an atmospheric or gaseousambient. This atmospheric or gaseous ambient prevents the metal of thefingers from being welded together.

It should be apparent that this invention will admit of modification,all without departing from the spirit of this invention.

I claim:
 1. In a generator including in combination a stator and arotor; a stub shaft of a generator power train connected to a source ofrotational power, said shaft rotating about an axis to provide poweredrotation of said rotor with respect to said stator to generateelectricity in windings disposed in said stator; a superconducting rotorincluding an outer rotor structure coaxial with an axis including meansfor damping electromotive forces from said stator to said rotor andmeans for supporting said means for damping electromotive forces againstelectromotive forces from said stator, and an inner rotor structurecoaxially disposed to said axis and within said outer rotor includingsuperconducting elements and means for cooling said superconductingelements, said inner rotor structure thermally insulated within saidouter rotor structure and subject to thermal excursion relative to saidouter rotor during cool down of said superconducting elements; and,means for axially and torsionally fixing said inner and outer rotorstructures together, and means for driving said rotor from said stubshaft, the improvement in said driving means comprising: a couplingextending between said inner rotor structure and said stub shaft, saidcoupling providing for longitudinal excursion and torsional rigiditybetween first and second ends of said coupling; said coupling includinga flexible diaphragm member attached to a first end of said coupling; aplurality of axially disposed fingers defining contacting surfacesparallel to said axis integrally attached to said flexible diaphragmmember, said fingers providing a rigid torsional connection to saiddiaphragm and extending axially of said rotating structures from thefirst end of said coupling toward the second end of said coupling; amember defining a corresponding plurality of spline receiving, axiallyextending slots for receiving fingers of said diaphragm attached to thesecond end of said coupling; means biasing said fingers relative to saidaxis with a force into said slots; said biasing fingers received withinsaid finger-receiving slots to slide with excursion of one of saidrotating structures with respect to the other rotating structure and toremain in nonslipping contact across said coupling during rotation ofsaid rotating structures with deflection of said inner rotatingstructure whereby non-axial loading forces of said inner rotatingstructure are elastically received at said flexible diaphragm duringrotation of said inner and outer rotating structures.
 2. The inventionof claim 1 and wherein said rotating structures at the end opposite fromsaid coupling are rigidly fixed together, and means for communicating acooling fluid to the interior of said inner rotating structure iscommunicated to the interior of said inner rotating structure.
 3. Theinvention of claim 1 and including means for drawing a vacuum about saidinner rotating structure; and said diaphragm member for isolating saidvacuum from said coupling.
 4. The invention of claim 1 and wherein saidmember defining a corresponding plurality of spline receiving, axiallyextending slots for receiving the fingers of said diaphragm member isattached to and defined within said stub shaft.
 5. A superconductingrotor having connection to a stub shaft of a generator power train, saidstub shaft rotating about an axis to provide powered rotation of saidrotor with respect to a stator to generate electricity in windingdisposed in a field of said stator, said superconducting rotorcomprising: an outer rotor structure coaxial with said axis includingmeans for damping electromotive forces from said stator to saidsuperconducting rotor and means for supporting said damping meansagainst said electromotive forces from said stator; an inner rotorstructure coaxially disposed to said axis and within said outer rotorincluding superconducting elements and means for cooling saidsuperconducting elements, said inner rotor structure thermally insulatedwithin said outer rotor structure and subject to thermal excursionrelative to said outer rotor during cool down of said superconductingelements; means for rigidly attaching axially and torsionally said innerand outer rotor structures together at one end; a flexible diaphragmattached to the other end of one of said rotor structures; a pluralityof axially disposed fingers defining outer contacting surfaces parallelto said axis integrally attached to said flexible diaphragm, saidfingers providing a rigid torsional connection to one of said rotorstructures at said other end and to transmit to said flexible diaphragma rigid, coaxial supporting force of one of said rotor structures atsaid other end; means for biasing said fingers relative to said axiswith a force at said outer contacting surfaces; means connecting saidstub shaft to said other rotor structure; said stub shaft defining acorresponding plurality of spline receiving, axially extending slots forreceiving the biased fingers of said flexible diaphragm; and, saidbiased fingers received within said finger receiving slots to slide withrespect to said stub shaft with thermal excursion of one of said rotorstructures with respect to said other rotor structure during cool downand to remain in non-slipping contact with said stub shaft duringon-line rotation of said rotor in said stator whereby non-axial loadingforces of said inner and outer rotor structures are elastically receivedat said flexible diaphragm during rotor rotation.
 6. The superconductingrotor of claim 5 and wherein said means for biasing said fingersincludes an inner surface of said fingers defining a frustroconicalconcavity; a frustroconical mandrel for being received within saidfingers; and a spring for biasing said mandrel into the frustroconicalcavity defined by said fingers to exhibit on said fingers a uniformoutwardly extending force.
 7. A superconducting rotor having connectionto a stub shaft of a generator power train, said stub shaft rotatingabout an axis to provide powered rotation of said rotor with respect toa stator to generate electricity in winding disposed in a field of saidstator, said superconducting rotor comprising: an outer rotor structurecoaxial with said axis including means for damping electromotive forcesfrom said stator to said rotor and means for supporting said dampingmeans against said electromotive forces from said stator; an inner rotorstructure coaxially disposed to said axis and within said outer rotorincluding superconducting elements and means for cooling saidsuperconducting elements, said inner rotor structure thermally insulatedwithin said outer rotor structure; means for rigidly attaching axiallyand torsionally said inner and outer rotor structures together at oneend; a flexible diaphragm closing the other end of said inner rotorstructure; a plurality of axially disposed fingers defining outercontacting surfaces parallel to said axis integrally attached to saidflexible diaphragm, said fingers providing a rigid torsional connectionto said inner rotor structure at said other end and to transmit to saidflexible diaphragm said coaxial supporting force of said inner rotor atsaid other end; said fingers defining at their combined axial exposedinner surfaces a frustroconical concavity; a frustroconical mandrelcomplementary to said frustroconical concavity of said fingers; meansfor biasing said frustroconical mandrel towards the apex of saidfrustroconical concavity to urge said fingers outwardly and away fromsaid axis with a uniform force at said outer contacting surfaces; meansconnecting said stub shaft to said outer rotor structure at the otherend of said outer rotor structure; a coaxial cylindrical concavity inthe outward end of said stub shaft exposed to said other end of saidinner rotor; said cylindrical concavity defining in the outwardperiphery thereof a plurality of spline receiving, axially extendingslots for receiving the outward biased fingers of said diaphragm; and,said outwardly biased fingers received within said spline receiving,axially extending slots to slide with respect to said stub shaft withthermal excursion of said inner rotor with respect to said outer rotorduring cool down and to remain in non-slipping contact with said stubshaft during on-line rotation of said rotor in said stator wherebynon-axial loading forces of said inner rotor are elastically received atsaid flexible diaphragm during rotor rotation.
 8. A generatorcomprising: a stator; a shaft of a generator power train, said shaftrotating about an axis to provide power rotation to a superconductingrotor with respect to said stator to generate electricity in the windingdisposed of said stator; a superconducting rotor including an outerrotor structure coaxial with an axis including means for dampingelectromotive forces from said stator to said rotor and means forsupporting said damping means from electromotive forces from said statorto said rotor; and an inner rotor structure coaxially disposed to saidaxis and within said outer rotor structure and including superconductingelements and means for cooling said superconducting elements, said innerrotor structure thermally insulated with respect to said outer rotorstructure and subject to thermal excursion relative to said outer rotorstructure during cool down of said superconducting elements; means foraxially and torsionally fixing said inner and outer rotor structurestogether at one end thereof; means for rigidly attaching one of saidrotor structures to said stub shaft for providing powered rotation forproviding power to both said structures; a flexible coupling extendingbetween said stub shaft and the other of said rotating structures, saidflexible coupling providing for longitudinal excursion and torsionalrigidity between said first and second ends of said coupling; saidcoupling including a flexible diaphragm member attached to a first endof said coupling; a plurality of axially disposed fingers defining outercontacting surfaces parallel to said axis integrally attached to saidflexible diaphragm member, said fingers providing a rigid torsionalconnection to said diaphragm member and extending axially of saidrotating structures from the first end of said coupling toward thesecond end of said coupling; a member defining a corresponding pluralityof spline receiving, axially extending slides for receiving fingers ofsaid diaphragm member attached to the second end of said couplings;means biasing said fingers received within said finger receiving slotsto slide with the excursion of one of said rotating structures withrespect to the other of said rotating structures and to remain innon-slipping contact across said coupling during rotation of saidrotating structures together whereby nonaxially loading forces on one ofsaid structures is elastically received at said flexible diaphragmmember during rotation of said inner and outer rotating structures. 9.The invention of claim 8 and wherein said flexible diaphragm member isattached across and encloses said inner rotating structure and saidmember defining a corresponding plurality of spline receiving, axiallyextending slots is attached to and defined within said rotating stepshaft.
 10. The invention of claim 8 and wherein said means for biasingsaid fingers biases said fingers outwardly with respect to said axis.11. The invention of claim 8 and wherein said means for biasing saidfingers includes said fingers defining at their combined axially exposedinner surfaces a frustroconical cavity; a frustroconical mandrelcomplementary to said frustroconical concavity of said fingers; andmeans for biasing said mandrel into the cavity of said fingers forapplying a uniform force on said fingers outwardly.
 12. A generatorcomprising: a stator; a shaft of a generator power train, said shaftrotating about an axis to provide power rotation of a superconductingrotor with respect to said stator to generate electricity in a windingdisposed in said stator, a superconducting rotor including an outerrotor structure coaxial with an axis including means for dampingelectromotive forces from said stator to said rotor and means forsupporting said damping means against said electromotive forces fromsaid stator, and an inner rotor structure coaxially disposed to saidaxis and within said outer rotor structure and including superconductingelements and means for cooling said superconducting elements, said innerrotor structure thermally insulated with respect to said outer rotorstructure and subject to thermal excursion relative to said outer rotorstructure during cool down of said superconducting elements; means foraxially and torsionally fixing said inner and outer rotor structurestogether at one end thereof; a flexible diaphragm member attached to theother end of one of said rotor structures; a plurality of axiallydisposed fingers defining outward contacting surfaces parallel to saidaxis integrally attached to said flexible diaphragm member, said fingersproviding a rigid torsional connection to one of said rotor structuresthrough said flexible diaphragm member and said other end and totransmit to said flexible diaphragm member rigid coaxial supportingsupports to one of said rotor structures at said other end; means forbiasing said fingers relative to said axis with the force at said othercontacting surfaces; means connecting said shaft to the other of saidrotor structures; said shaft defining a corresponding plurality ofspline receiving, axially extending slots for receiving biased fingersof said diaphragm member; and, said biased fingers received within saidfinger receiving slots to slide with respect to said shaft for thermalexcursion of one of said rotor structures with respect to the other ofsaid rotor structures during cool down and to remain in non-slippingcontact with said stub shaft during on-line rotation of said rotor insaid stator whereby non-axial loading forces of said inner rotor areelastically received at said flexible diaphragm member during rotorrotation.